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Re: Garage Floor Design

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+ACI-Does anybody know something that I am missing here. Could there be a
justification for using less than 1000+ACM- on a single joist?+ACI-

This is a good question.  I will be curious to see how others deal with

The Caltrans bridge manual uses a S/4 distribution for timber beams with
planks.  The S is the stringer spacing, in this case one foot would result
in four joists supporting the point load.  Planks are defined as +ACI-pieces of
lumber laid edge to edge with the wide faces bearing on the supports+ACI- (I am
assuming 4x material min), or four inch thick nail laminated (on edge).  I
cannot find any reference in the bridge manual to plywood with concrete in
place of planks.

APA report +ACM-139 covers plywood floors for residential garages.  They make
recommendations for floors both with and without concrete topping.  For
example: 1 1/8+ACI- ply with 3+ACI- of concrete (6x6x10 ww mesh) spans 24+ACI-,  3/4+ACI-
ply w/ 3+ACI- of concrete spans 16+ACI-.  I have a gut feeling that the 3/4+ACI- plywood
with a 3+ACI- slab would be equivalent to the 4x planks in terms of being able
to distribute wheel loads.  If my assumption is correct then it would seem
me that you could use 500+ACM- on a single joist.

Randy Vogelgesang S.E.

-----Original Message-----
Date: Thursday, November 19, 1998 10:24 PM
Subject: Re: Garage Floor Design

+AD4-I've been called to investigate a residential garage floor to see whether
+AD4-additional weight over the raised garage floor was possible.
+AD4-The problem was that the garage was at the end of a long down-sloping,
+AD4-steep driveway with a 6+ACI- trench drain, 3' away from the garage door and
+AD4-level beyond the trench to the garage. Originally, the concrete level
+AD4-and just outside the garage where at the same level (big mistake). Then,
+AD4-1/2+ACI- pavers were placed on top of the driveway slab. This made the
+AD4-worse by letting water flow into the garage floor.
+AD4-A waterproofing contractor wants to raise the garage floor level by adding
+AD4-leveling concrete topping on the existing floor ( The most economical way,
+AD4-short of reinforcing the floor joist or reworking the approch to the
+AD4-The garage floor consists of 4+ACI- regular concrete reinforced with +ACM-5 bars +AEA-
+AD4-16+ACI-, over 1-1/8+ACI- plywood, over 14+ACI- TJI/35 +ACI-Residential Silent Floor+ACI- joists
+AD4-12+ACI- o.c.,
+AD4-spaning 20'.
+AD4-My preliminary calculations indicate that the floor is underdesigned as it
+AD4-when considering the minimum 2000+ACM- concentrated load distributed over
+AD4-area along with uniform dead load ( the 50+ACM-/sf live load works). I use
+AD4-concentrated load per joist for shear and bending, assuming the 2000+ACM- will
+AD4-shared by two or more joists (Some plan checkers question the use of 1000+ACM-
+AD4-instead of 2000+ACM- +ACEAIQAh-).
+AD4-Does anybody know somthing that I am missing here. Could there be a
+AD4-justification for using less than 1000+ACM- on a single joist?
+AD4-To make the responses short, I am looking for an answer to my question
+AD4-regarding the use of less than 1000+ACM- concentrated load per joist.
+AD4-Oshin Tosounian, S.E.